1. Field of the Invention
The invention pertains to an expressing or dispensing device for a coaxial cartridge, and to the combination of a coaxial cartridge with a novel expressing device.
2. Prior Art
Coaxial cartridges of the aforementioned type are frequently utilized for storing and processing reactive adhesives, sealing compounds and the like. Such coaxial cartridges usually contain an outer tube and an inner tube that is arranged coaxial to the outer tube, wherein said tubes delimit an inner chamber and an outer chamber for accommodating the different components. However, special expressing rams need to be provided in order to express coaxial cartridges of this type with the broadly utilized and inexpensive standard metering guns for single-component cartridges. Commercially available standard metering guns have a pressure ram that would prevent the contents of the cartridge from being expressed once the ram contacts the inner tube. This is the reason that a specially designed pressure ram needs to be utilized which consists of a central pressure ram and an outer pressure ram in the form of a tube. The disadvantage of this construction can be seen in the fact that the expressing ram occupies approximately half of the space available for accommodation of the cartridge and the expressing ram in a standard metering gun. Consequently, the filling volume of such coaxial cartridges must be limited to half the filling volume of commercially available single-component cartridges.
It has also been proposed to realize the inner tube of a coaxial cartridge in the form of a folding aluminum tube, such that the inner tube is folded up when the coaxial cartridge is expressed with a commercially available metering gun for single-component cartridges. However, this embodiment has the disadvantage that filling with resinous substances and installation of the piston are subject to special requirements. Coaxial cartridges consisting of plastic and metal parts are also not ideal with respect to their disposal.